阅读说明：本技术 循环利用地热能进行冬季保温的人工湿地系统及方法 (Constructed wetland system and method for conducting heat preservation in winter by recycling geothermal energy ) 是由 韩延成 王月蕾 周欣悦 方攀博 陈思涵 黄兆虎 王栋 于 2021-08-05 设计创作，主要内容包括：本发明公开了一种循环利用地热能进行冬季保温的人工湿地系统及方法,人工湿地包括湿地基质、污水进口、污水出口、水暖管道和地下含水层,所述水暖管道铺设在湿地基质中,水暖管道的进水口位于湿地基质的上部,水暖管道的出水口位于湿地基质的下部；所述湿地基质的上部和下部分别设置有污水进水口和污水出水口；所述湿地基质至少包括土壤层、人工混合层和沸石层,所述土壤层上方种植湿地植物,土壤层、人工混合层和沸石层中分别设置有首尾相接的第一水暖管道、第二水暖管道和第三水暖管道,且第一水暖管道的进水口输入地下热水,第三水暖管道的出水口将冷水输入地下含水层。本发明能够保证冬季湿地内更高的温度,从而具有更高的污染物去除率。(The invention discloses an artificial wetland system and a method for carrying out heat preservation in winter by recycling geothermal energy, wherein the artificial wetland comprises a wetland substrate, a sewage inlet, a sewage outlet, a water heating pipeline and an underground aquifer, the water heating pipeline is laid in the wetland substrate, a water inlet of the water heating pipeline is positioned at the upper part of the wetland substrate, and a water outlet of the water heating pipeline is positioned at the lower part of the wetland substrate; the upper part and the lower part of the wetland substrate are respectively provided with a sewage inlet and a sewage outlet; the wetland substrate at least comprises a soil layer, an artificial mixed layer and a zeolite layer, wetland plants are planted above the soil layer, a first water heating pipeline, a second water heating pipeline and a third water heating pipeline which are connected end to end are respectively arranged in the soil layer, the artificial mixed layer and the zeolite layer, the water inlet of the first water heating pipeline is used for inputting underground hot water, and the water outlet of the third water heating pipeline is used for inputting cold water into the underground water-containing layer. The invention can ensure higher temperature in the wetland in winter, thereby having higher pollutant removal rate.)

1. An artificial wetland system for conducting winter heat preservation by recycling geothermal energy is characterized by comprising a wetland substrate, a sewage inlet, a sewage outlet water heating pipeline and an underground aquifer, wherein the water heating pipeline is laid in the wetland substrate, a water inlet of the water heating pipeline is positioned at the upper part of the wetland substrate, and a water outlet of the water heating pipeline is positioned at the lower part of the wetland substrate; the upper part and the lower part of the wetland substrate are respectively provided with a sewage inlet and a sewage outlet;

the wetland matrix includes soil horizon, artificial mixing layer and zeolite layer at least, wetland plant is planted to soil horizon top, is provided with first hot-water heating pipeline in the soil horizon, and the artificial mixing layer is provided with second hot-water heating pipeline, the zeolite layer is provided with third hot-water heating pipeline, first hot-water heating pipeline, second hot-water heating pipeline and third hot-water heating pipeline end to end, and the water inlet of first hot-water heating pipeline inputs underground hot water, and the delivery port of third hot-water heating pipeline inputs cold water underground water-containing layer.

2. The artificial wetland system of claim 1, wherein the water inlet of the first water heating pipeline and the water outlet of the third water heating pipeline are respectively positioned at two sides of the wetland substrate.

3. The constructed wetland system of claim 1, wherein the sewage inlet and the sewage outlet are respectively positioned at two sides of the wetland substrate.

4. The artificial wetland system of claim 1, wherein the water heating pipes are made of a heat conductive material, the interval between the water pipes of the first water heating pipe is smaller than that of the second water heating pipe, and the interval between the water pipes of the third water heating pipe is larger than that of the second water heating pipe.

5. The constructed wetland system of claim 1, wherein the wetland plants are calamus plants.

6. The constructed wetland system of any one of claims 1 to 5, further comprising an underground hot water delivery device and a cold water delivery device, wherein one end of the underground hot water delivery device is arranged in an underground aquifer, and the other end of the underground hot water delivery device is communicated with the water inlet of the first water heating pipeline; one end of the cold water conveying device is communicated with a water outlet of the third water heating pipeline, and the other end of the cold water conveying device is arranged in the underground aquifer; underground hot water after the underground hot water conveying device is heated by means of geothermal energy is pumped to the water heating pipeline from the underground water-containing layer through a water inlet of the water heating pipeline, the underground hot water is heated for the artificial wetland through pipeline circulation, then circulating cold water is refilled to the underground water-containing layer from a water outlet of the water heating pipeline through the cold water conveying device, and the underground water-containing layer is heated by means of geothermal energy and is recycled.

7. The constructed wetland system of claim 6, wherein the underground hot water delivery device comprises a suction well and the cold water delivery device comprises a recharge well.

8. The constructed wetland system of claim 6, wherein the underground hot water delivery device and the cold water delivery device have the same water delivery amount.

9. The constructed wetland system of any one of claims 1 to 5, wherein the water inlet of the first water heating pipeline is used for inputting underground hot water by receiving water from a spring or a karst well.

10. A method for performing winter insulation by recycling geothermal energy, which is characterized in that the artificial wetland system of any one of claims 1 to 8 is used for performing winter insulation by recycling geothermal energy, and the method comprises the following steps:

pumping underground hot water heated by the geothermal energy from an underground aquifer to a water inlet of the wetland water heating pipeline;

the underground hot water is circulated in the water heating pipeline to heat the artificial wetland;

the circulated cold water is refilled to the underground aquifer from the water outlet of the water heating pipeline;

in the process of heating the artificial wetland, sewage is input into the artificial wetland through the sewage inlet, and is discharged through the sewage outlet after being treated by the artificial wetland.

Technical Field

The invention relates to an artificial wetland system and an artificial wetland method for carrying out winter heat preservation by recycling geothermal energy, belonging to the technical field of sewage treatment.

Background

The artificial wetland has wide application prospect in such areas due to the technical advantages of low cost and easy maintenance. At present, the artificial wetland is proved to be an economic and effective means for treating domestic sewage, and has been widely applied at home and abroad, so that the artificial wetland has a relatively ideal effect and becomes one of the mainstream processes for treating the domestic sewage.

The artificial wetland system is a sewage treatment system simulating a natural wetland ecosystem, and mainly realizes the purpose of sewage purification by means of a series of reactions such as physics, chemistry, biology, microorganism and the like. In cold areas in the north, the temperature drops below zero in winter, the water surface can freeze, and the sewage treatment effect is poor or the artificial wetland cannot normally operate no matter the artificial wetland is subsurface flow or surface flow, so that the popularization and the use of the artificial wetland in the north are limited. The removal capability of the constructed wetland to nitrogen and phosphorus pollutants is weakened under the influence of low temperature in winter, withering and death of wetland plants and reduction of the activity of nitrogen-releasing microorganisms. Research shows that when the temperature is lower than 4 ℃, the nitrification and denitrification of microorganisms are basically stopped, and the removal effect of the artificial wetland on pollutants is poor. Therefore, how to improve the removal efficiency of the artificial wetland on the pollutants in winter becomes a problem to be solved urgently.

The known artificial wetland winter heat preservation method comprises an icing method, a straw covering method, a pig manure and reed composting method, a mulching film method, a greenhouse temperature method and the like. The icing method is to add an ice layer, straw and other isolation layers on the surface of the subsurface flow wetland to prevent the artificial wetland from being frozen, but the removal rates of TN and TP by the wetland are only 25% and 35% respectively; the mulching film method is to cover a mulching film on the surface of the wetland, so that the ammonia nitrogen removal efficiency of the wetland is effectively improved, but the removal rate of COD, TN and NH4+ -N is not high. The pig manure and reed composting method cannot be applied to large-area wetlands because the survival life of the wetlands is about 40 days. The straw covering method is to adopt the harvested plants to cover and preserve the heat of the artificial wetland under the low-temperature condition in winter, but the removal rate of TP and NH4+ -N, TN is only 31.4 percent, 26.5 percent and 9.6 percent, and the removal effect of the straw covering method is only respectively improved by 15.5 percent, 9.7 percent and 5.0 percent compared with the removal effect of the artificial wetland without the harvested plants.

It can be seen that these methods have very limited ability to raise wetland temperature, resulting in low contaminant removal rates. The straw mulching method, the pig manure and reed composting method and the mulching film mulching method can cause secondary environmental pollution, and the greenhouse warming method has high construction cost and difficult maintenance and is not suitable for wide application. In addition, the temperature can not be controlled artificially by the methods, so that the wetland can still be frozen, plants or microorganisms can die when the temperature is very low in winter or low temperature and cloudy days continue for a long time, and the wetland can not run or the decontamination capability is greatly reduced. Therefore, the existing artificial wetland heat preservation method in winter is not only incapable of completely removing organic matters and nitrogen and phosphorus in sewage, but also high in cost and not suitable for wide popularization.

Disclosure of Invention

In order to solve the problems, the invention provides an artificial wetland system and an artificial wetland method for carrying out winter heat preservation by recycling geothermal energy, which can effectively improve the temperature of the wetland and the removal rate of pollutants of the wetland in winter, and utilize pollution-free geothermal energy with low cost.

The technical scheme adopted for solving the technical problems is as follows:

in a first aspect, the artificial wetland system for conducting winter heat preservation by recycling geothermal energy provided by the embodiment of the invention comprises a wetland substrate, a sewage inlet, a sewage outlet, a water heating pipeline, an underground hot water conveying device, a cold water conveying device and an underground aquifer, wherein the water heating pipeline is laid in the wetland substrate, a water inlet of the water heating pipeline is positioned at the upper part of the wetland substrate, and a water outlet of the water heating pipeline is positioned at the lower part of the wetland substrate; the upper part and the lower part of the wetland substrate are respectively provided with a sewage inlet and a sewage outlet;

the wetland matrix includes soil horizon, artificial mixing layer and zeolite layer at least, wetland plant is planted to soil horizon top, is provided with first hot-water heating pipeline in the soil horizon, and the artificial mixing layer is provided with second hot-water heating pipeline, the zeolite layer is provided with third hot-water heating pipeline, first hot-water heating pipeline, second hot-water heating pipeline and third hot-water heating pipeline end to end, and the water inlet of first hot-water heating pipeline inputs underground hot water, the delivery port of third hot-water heating pipeline will circulate the cold water input underground water-containing layer.

As a possible implementation manner of this embodiment, the water inlet of the first water heating pipeline and the water outlet of the third water heating pipeline are respectively located at two sides of the wetland substrate.

As a possible implementation manner of this embodiment, the sewage inlet and the sewage outlet are respectively located at two sides of the wetland substrate.

As a possible implementation manner of this embodiment, the water heating pipes are made of a material having good thermal conductivity, the interval between the water pipes of the first water heating pipe is smaller than the interval between the water pipes of the second water heating pipe, and the interval between the water pipes of the third water heating pipe is larger than the interval between the water pipes of the second water heating pipe.

As a possible implementation manner of this embodiment, the wetland plant is a calamus plant.

As a possible implementation manner of this embodiment, the artificial wetland is a movable small wetland structure or a large wetland structure.

As a possible implementation manner of the embodiment, the artificial wetland is arranged below the ground surface or above the ground surface.

As a possible implementation manner of this embodiment, the water inlet and the water outlet of the water heating pipeline are respectively provided with a water inlet control valve and a water outlet control valve.

As a possible implementation manner of this embodiment, the artificial wetland system further includes an underground hot water delivery device and a cold water delivery device, one end of the underground hot water delivery device is disposed in the underground aquifer, and the other end of the underground hot water delivery device is communicated with the water inlet of the first water heating pipeline; one end of the cold water conveying device is communicated with a water outlet of the third water heating pipeline, and the other end of the cold water conveying device is arranged in the underground aquifer; underground hot water after the underground hot water conveying device is heated by means of geothermal energy is pumped to the water heating pipeline from the underground water-containing layer through a water inlet of the water heating pipeline, the underground hot water is heated for the artificial wetland through pipeline circulation, then circulating cold water is refilled to the underground water-containing layer from a water outlet of the water heating pipeline through the cold water conveying device, and the underground water-containing layer is heated by means of geothermal energy and is recycled.

As a possible implementation manner of this embodiment, the underground hot water delivery device includes a pumping well, and the cold water delivery device includes a recharging well.

As a possible implementation manner of this embodiment, the water delivery amount of the underground hot water delivery device and the water delivery amount of the underground cold water delivery device are equal.

As a possible implementation manner of this embodiment, the water inlet of the first water heating pipeline is used for inputting underground hot water by receiving water from a spring or a karst well.

In a second aspect, an embodiment of the present invention provides a method for performing winter insulation by recycling geothermal energy, where the method for performing winter insulation by recycling geothermal energy using the artificial wetland system includes:

pumping underground hot water heated by the geothermal energy from an underground aquifer to a water inlet of the wetland water heating pipeline;

the underground hot water is circulated in the water heating pipeline to heat the artificial wetland;

the circulated cold water is refilled to the underground aquifer from the water outlet of the water heating pipeline;

in the process of heating the artificial wetland, sewage is input into the artificial wetland through the sewage inlet, and is discharged through the sewage outlet after being treated by the artificial wetland.

The technical scheme of the embodiment of the invention has the following beneficial effects:

the invention provides an artificial wetland for carrying out winter heat preservation by recycling geothermal energy, which can ensure higher temperature in the wetland in winter, thereby having higher pollutant removal rate; the invention reuses clean geothermal energy, and can not cause secondary pollution of other methods such as straw covering, pig manure composting, mulching film covering and the like; the underground hot water heats the wetland through the water heating pipeline in the wetland, so that the underground hot water is isolated from the wetland, the pollution of underground water is avoided, the temperature of the wetland can be controlled within a certain range, the water pumping quantity can be increased when the temperature is lower, and the water pumping quantity can be reduced when the temperature is higher, so that the temperature is controlled, and the wetland is ensured not to be frozen. And the pumping of underground water is stopped directly in summer; compared with the method of covering by straws and the like, the artificial wetland does not need to be replaced every year, can be applied for a long time, and has low cost because the water pumping cost is mainly used in the operation process. The underground hot water delivery device and the cold water delivery device have the same water delivery amount, namely the water pumping amount (underground water) is equal to the amount of water which is re-filled into an underground aquifer, so that the balance of the underground water can be ensured.

Description of the drawings:

fig. 1 is a block diagram illustrating an artificial wetland system for winter insulation by recycling geothermal energy according to an exemplary embodiment;

fig. 2 is a view showing an on-site simulation of an artificial wetland system for winter heat preservation by recycling geothermal energy according to an exemplary embodiment;

FIG. 3 is a flow chart illustrating a method for winter proofing using geothermal energy in a cycle, according to an exemplary embodiment.

Detailed Description

The invention is further illustrated by the following examples in conjunction with the accompanying drawings:

in order to clearly explain the technical features of the present invention, the following detailed description of the present invention is provided with reference to the accompanying drawings. The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. It should be noted that the components illustrated in the figures are not necessarily drawn to scale. Descriptions of well-known components and processing techniques and procedures are omitted so as to not unnecessarily limit the invention.

Fig. 1 is a structural view illustrating an artificial wetland system for winter insulation by recycling geothermal energy according to an exemplary embodiment. The constructed wetland system for conducting winter heat preservation by recycling geothermal energy comprises a wetland substrate, a water heating pipeline 1 and an underground aquifer 2, wherein the water heating pipeline 1 is laid in the wetland substrate, a water inlet 3 of the water heating pipeline is positioned at the upper part of the wetland substrate, and a water outlet 4 of the water heating pipeline is positioned at the lower part of the wetland substrate; the upper part and the lower part of the wetland matrix are respectively provided with a sewage inlet 5 and a sewage outlet 6;

the artificial wetland system effectively improves the temperature of the wetland, improves the removal rate of pollutants of the wetland in winter, utilizes pollution-free geothermal energy and has low cost.

Wetland matrix is from the top down for soil horizon 7, artificial mixing layer 8 and zeolite layer 9 in proper order, wetland plant 10 is planted to soil horizon 7 top, is provided with first hot-water heating pipeline in the soil horizon 7, and artificial mixing layer 8 is provided with second hot-water heating pipeline, zeolite layer 9 is provided with third hot-water heating pipeline, first hot-water heating pipeline, second hot-water heating pipeline and third hot-water heating pipeline connect end to end, and the water inlet of first hot-water heating pipeline inputs underground hot water, and cold water input underground aquifer is gone into to the delivery port of third hot-water heating pipeline.

As a possible implementation manner of this embodiment, the soil layer is mainly soil; the artificial mixed layer comprises one or a combination of more of fine sand, coarse sand, ash and limestone; the zeolite layer is mainly zeolite. The wetland substrate of the invention can be provided with a gravel layer and the like according to the needs besides the soil layer 7, the artificial mixed layer 8 and the zeolite layer 9.

As a possible implementation manner of this embodiment, the particle size in the soil layer 7, the artificial mixed layer 8, and the zeolite layer 9 gradually increases from top to bottom.

As a possible implementation manner of this embodiment, the water inlet of the first water heating pipeline and the water outlet of the third water heating pipeline are respectively located at two sides of the wetland substrate.

As a possible implementation manner of this embodiment, the sewage inlet and the sewage outlet are respectively located at two sides of the wetland substrate.

As a possible implementation manner of this embodiment, the water heating pipes are made of a heat conductive material, the water pipe interval of the first water heating pipe is smaller than the water pipe interval of the second water heating pipe, and the water pipe interval of the third water heating pipe is larger than the water pipe interval of the second water heating pipe. The hot-water heating pipeline has the material of good heat conductivity to make, and it is denser (vertical interval is less) in upper plant roots district when laying, and the lower floor is comparatively sparse (vertical interval is great), so both can guarantee the temperature in plant roots district, avoids the plant to freeze and dies, and the wetland top layer is frozen when also can prevent that the air temperature is lower.

As a possible implementation manner of this embodiment, the wetland plant is a calamus plant with a relatively thick root system, and the pores in the artificial wetland can be increased, so that the water holding volume of the artificial wetland is increased, phosphorus in the water body can react for a relatively long time, and the removal rate of the artificial wetland system to TP is increased.

As a possible implementation manner of this embodiment, the artificial wetland is a movable small wetland structure or a large wetland structure.

As a possible implementation manner of the embodiment, the artificial wetland is arranged below the ground surface or above the ground surface.

As a possible implementation manner of this embodiment, the water inlet and the water outlet of the water heating pipeline are respectively provided with a water inlet control valve and a water outlet control valve.

As a possible implementation manner of this embodiment, the artificial wetland system further includes an underground hot water delivery device and a cold water delivery device, one end of the underground hot water delivery device is disposed in the underground aquifer, and the other end of the underground hot water delivery device is communicated with the water inlet of the first water heating pipeline; one end of the cold water conveying device is communicated with a water outlet of the third water heating pipeline, and the other end of the cold water conveying device is arranged in the underground aquifer; underground hot water after the underground hot water conveying device is heated by means of geothermal energy is pumped to the water heating pipeline from the underground water-containing layer through a water inlet of the water heating pipeline, the underground hot water is heated for the artificial wetland through pipeline circulation, then circulating cold water is refilled to the underground water-containing layer from a water outlet of the water heating pipeline through the cold water conveying device, and the underground water-containing layer is heated by means of geothermal energy and is recycled.

As a possible implementation manner of this embodiment, the underground hot water delivery device includes a pumping well, and the cold water delivery device includes a recharging well.

As a possible implementation manner of this embodiment, the water delivery amount of the underground hot water delivery device and the water delivery amount of the underground cold water delivery device are equal.

As a possible implementation manner of this embodiment, the water inlet of the first water heating pipeline can also input underground hot water through water of a fountain or a karst well.

Fig. 2 is a view showing an on-site simulation of an artificial wetland system for winter heat preservation by recycling geothermal energy according to an exemplary embodiment. As shown in fig. 2, the artificial wetland system comprises a pumping well, a recharging well, an underground hot water inlet, a cold water outlet after wetland circulation, a sewage inlet, a sewage outlet, wetland substrates, a water heating pipeline in the wetland, wetland plants, an underground aquifer and the like. The pumping well is communicated with the underground aquifer, pumps underground hot water through a water pump, is communicated with a water inlet through which the underground hot water enters the wetland, is communicated with a water heating pipeline in the wetland, is communicated with a water outlet through which cold water circulates in the wetland, is communicated with the recharging well, and finally recharges the cold water to the underground aquifer. The water heating pipeline in the wetland is made of materials with good heat conductivity, and when the water heating pipeline is laid, the upper layer plant root area is dense (the vertical distance is small), and the lower layer plant root area is sparse (the vertical distance is large); the underground hot water inlet and the underground hot water outlet are arranged on two sides of the wetland, the sewage inlet and the sewage outlet are respectively arranged on two sides of the wetland, and the inlet is higher than the outlet. The substrate comprises a soil layer, an artificial mixing layer, a zeolite layer and the like from top to bottom. The wetland plants are mainly cold-resistant plants such as calamus and the like which are suitable for wetland growth in winter. The underground hot water can enter the wetland through a pumping well, and can also enter a water inlet and a circulating pipeline of the wetland through spring, karez and the like by gravity flow. The wetland can be a movable small wetland or a large wetland.

In the water heating pipeline system in the artificial wetland, the pumping well is utilized to pump underground water heated by underground shallow geothermal energy to the water heating pipeline system laid in the artificial wetland, the artificial wetland is heated by pipeline circulation, then the circulated cold water is refilled to an underground water-bearing layer through the refilling well, then the underground shallow geothermal energy is utilized for heating, and then the pumping well is utilized to pump underground hot water to the water heating pipeline system laid in the artificial wetland for recycling the geothermal energy.

As shown in fig. 3, the method for performing winter insulation by recycling geothermal energy according to the embodiment of the present invention, which uses the artificial wetland system to perform winter insulation by recycling geothermal energy, includes the following steps:

pumping underground hot water heated by geothermal energy from an underground aquifer to a water heating pipeline through a water inlet of the water heating pipeline;

the underground hot water is circulated to the artificial wetland through the pipeline for heating;

the circulated cold water is refilled to the underground aquifer from the water outlet of the water heating pipeline;

in the process of heating the artificial wetland, sewage is input into the artificial wetland through the sewage inlet, and is discharged through the sewage outlet after being treated by the artificial wetland.

The artificial wetland for conducting winter heat preservation by recycling geothermal energy can ensure higher temperature in the wetland in winter; the underground water heats the wetland through the pipeline and is isolated from the wetland, so that the pollution of the underground water is avoided, and secondary pollution of compost, rice straws (wheat straws), plastic films and the like is also avoided; the temperature of the wetland can be controlled within a certain range, when the temperature is lower, the water pumping quantity can be increased, and when the temperature is higher, the water pumping quantity can be reduced; compared with straw covering and other methods, the system does not need to be replaced every year, can be applied for a long time, is mainly used for pumping water in the operation process, and is low in cost.

In order to verify the artificial wetland system, the applicant constructs two small artificial wetlands, wherein one small artificial wetland is a common control group artificial wetland (hereinafter referred to as a control group) and the other small artificial wetland is an artificial wetland with a water heating pipeline experimental group (hereinafter referred to as an experimental group) laid in the artificial wetland.

The experimental device consists of a water collecting tank, an NKP peristaltic pump, a heating water barrel and a vertical flow artificial wetland. The sizes of the experimental group wetland and the control group wetland are both 0.5m multiplied by 0.35m multiplied by 0.32m, and the effective volume is 50L. The gradient of the bottom surface of the wetland is 1 percent.

During construction, water heating pipelines are paved in the wetland in a layered mode (the wetland is three layers, and the water heating pipelines adopt iron pipes plated with antirust paint). Because the temperature of the wetland is mainly determined by the temperature of water entering the pipeline, and is not related to whether water is pumped from the underground or not, the invention adopts the electric tracing band to heat water to replace underground water. Meanwhile, an SN-NTC10 temperature controller is used for temperature monitoring, so that the temperature is kept at 18 ℃, and the temperature is in accordance with the temperature of shallow groundwater in Jinan city. When the wetland heating device operates, hot water enters the wetland through the water inlet, heats the wetland through the water heating pipeline and flows out of the water outlet. Collecting the water flowing out from the water heating pipeline for reheating and recycling. The hot water is not exchanged with the wetland. Meanwhile, sewage is pumped into the wetland through the NKP peristaltic pump and flows out from the sewage outlet.

The experiment starts from 11 months and ends at the bottom of 2 months, the experimental water inlet time is 08: 00-20: 00, and 10L of water is fed every day. Before the experiment begins, clear water is firstly introduced into the constructed wetland for debugging and running, sampling is carried out every 3 days after the experiment pool runs stably, the water sample is immediately sent into a laboratory after being collected, and parallel samples are made for analyzing COD and NH₄ ⁺-N, TP, etc.

The removal efficiency of the artificial wetland to COD is as follows:

through the test, the removal rate of COD in the sewage is determined by the experimental group and the control group as follows. The COD of the inlet water of the two artificial wetlands is kept at 125mg/L, and the hydraulic retention time is kept at 3 d. The COD content in the water sample at the water outlet of the experimental group is 41.68 +/-3.44 mg/L, and the removal rate reaches 69.41 percent at most during the test period. Compared with the COD content in the water outlet of the control group of 69.71 +/-9.60 mg/L, the removal rate of the COD is 51.91 percent at most. Along with the gradual reduction of the temperature, the removal efficiency of the control group to COD is gradually reduced until the control group wetland is frozen and cannot be operated. However, the removal effect of the experimental group was stable. In winter, the removal efficiency of COD by the experimental group is higher than that by the control group, and the removal efficiency is improved by 17.50%. Therefore, the efficiency of removing COD by the artificial wetland can be improved by heating the artificial wetland by using geothermal energy in winter.

The removal effect of the artificial wetland on NH4+ -N is as follows:

through tests, the experimental group has a winter water outlet NH₄ ⁺The concentration of-N is 12.05 +/-1.15 mg/L, the removal rate reaches 50.45% at most, and is compared with that of NH at a water outlet of a control group₄ ⁺The concentration of-N is 18.37 +/-1.49 mg/L, and the removal efficiency is 23.27 percent at most. Experimental group to NH₄ ⁺The removal effect of-N is improved by 27.18 percent compared with the control group. As can be seen, NH in the constructed wetland₄ ⁺The removal effect of-N is greatly influenced by temperature, the temperature is gradually reduced along with the change of seasons, and the wetland system is used for removing NH₄ ⁺The poorer the removal effect of-N, until the control wetland is frozen, and the control wetland cannot be operated. Experiments prove that the heating of the artificial wetland by using geothermal energy can effectively improve the NH content of the artificial wetland in winter₄ ⁺-removal efficiency of N.

The TP removal effect of the constructed wetland is as follows:

through tests, the concentration of the discharged water of phosphorus is 1.34 +/-0.23 mg/L, the removal efficiency is up to 69.17% at most, and the removal effect is good. The TP removal effect of the control group is poor, the effluent concentration is 2.87 +/-0.25 mg/L, the removal efficiency is 27.22 percent at most, the removal rate is reduced along with the reduction of the temperature until the control group wetland is frozen and the control group wetland cannot run. By comparison, the TP removal efficiency of the experimental group is 41.95% higher than that of the control group. Along with the reduction of the temperature, the biological activity of wetland plants is reduced under the condition that no heat preservation measure is adopted, so that the TP removal effect of the artificial wetland is poor. Experiments prove that the TP removal efficiency of the artificial wetland in winter can be effectively improved by heating the artificial wetland by using geothermal energy.

The invention has the following characteristics: (1) pumping the underground water heated by shallow geothermal energy to a water heating pipeline system laid in the artificial wetland, heating the artificial wetland by circulation, and finally recharging the circulated cold water to an underground aquifer through a recharging well for recycling. The wetland has the advantages that: (1) geothermal energy can be repeatedly utilized; (2) the underground water heats the wetland through the pipeline and is isolated from the wetland, so that the pollution of the underground water is avoided. (3) The temperature of the wetland can be controlled within a certain range, when the temperature is lower, the water pumping quantity can be increased, and when the temperature is higher, the water pumping quantity can be reduced, so that the temperature is controlled; (4) compared with the straw covering method and the like, the system does not need to be replaced every year, can be applied for a long time, is mainly used for pumping water in the operation process, and is low in cost; (5) the water heating circulation pipelines in the wetland of the system are densely distributed in the upper plant root system area and sparsely distributed in the lower plant root system area. (6) The wetland utilizing the geothermal energy can ensure higher temperature in the wetland in winter, thereby having higher pollutant removal rate.

The artificial wetland system has an aerobic environment and an anaerobic environment, aerobic bacteria and anaerobic bacteria are respectively subjected to nitrification and denitrification reactions, and the higher the reaction degree is, the artificial wetland system can carry out NH reaction₄ ⁺The better the removal of-N and vice versa. Because the temperature in cold regions is low, the surface temperature of many regions reaches below 0 ℃, so that the artificial wetland plants cannot grow normally, and the nitrifying and denitrifying bacteria in the wetland system lose the biological activity, thereby hindering the ammoniation and nitrification. Thus ensuring a suitable temperature for the microorganisms to have normal biological activity on NH₄ ⁺The removal of-N plays a very important role. The invention ensures the wetland to have higher temperature by utilizing the geothermal energy, ensures the normal survival of wetland plants and microorganisms, and ensures the nitrification and denitrification reaction of aerobic bacteria and anaerobic bacteria, thereby carrying out the nitrification and denitrification reaction on NH₄ ⁺N has good removal effect.

The removal of TP by the artificial wetland system depends on two factors, one of which is that the plant absorbs the TP by itself to remove phosphorus in the sewage; therefore, the temperature of the artificial wetland system is heated, the growth of plant roots is promoted, and the removal of phosphorus can be promoted. And secondly, removing phosphorus element in the sewage through microorganism accumulation and physical action of the artificial wetland matrix. Therefore, the artificial wetland plant selects the calamus with a thicker root system and properly enlarges the pores in the artificial wetland, so that the water containing volume of the artificial wetland is increased, and the phosphorus in the water body can react for a longer time and is better adsorbed by the artificial wetland system. The invention ensures the wetland to have higher temperature by utilizing the geothermal energy, so that wetland plants can normally survive, microorganisms can normally accumulate, and the removal of TP by the artificial wetland system is facilitated. In addition, the artificial wetland plant of the invention selects the calamus with a thicker root system to enlarge the pores in the artificial wetland, so that the water containing volume of the artificial wetland is enlarged, the phosphorus in the water body can react for a longer time, and the removal rate of the artificial wetland system to TP is increased.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.